The design of the 165LS is quite different (complex) to its shorter 90mm brother. The leaf shutter is useable in the circumstances for which it was designed (flash sync at all speeds), perfectly so, just
not with MLU, with leaf shutter mode engaged. With leaf shutter mode disengaged, the 165LS acts like a big, fat, round telephoto (and a bloody good one at that). Engage leaf shutter mode, connect a flash circuit and presto! You have bragging rights. Big time.
You cannot use the leaf shutter only/independently of the 67 shutter.
Be aware that with either LS lens, and leaf shutter mode engaged, there will be no viewfinder image: the mirror is
not up, but the leaf shutter is cocked. Camera shutter fires first, then LS.